There are two conventional ways to retain partial dentures. In clasp type attachments or direct retainers, metal retentive clasps are formed in the base of the denture. The clasps snap downwardly over selected teeth and engage the undercut area of the tooth.
There are numerous drawbacks to clasp type partial dentures. First, clasp type partial dentures require the presence of strong teeth since they place great stress on teeth to which the clasps are secured. The clasps cannot be secured to weak or questionable teeth. Secondly, the retentive clasps can be irritating or uncomfortable to the denture wearer making their use an unattractive alternative.
Precision retainers are also commonly used to secure partial dentures. Precision retainers employ snap connectors secured to an existing tooth structure by means of a cap, bridge, etc. A mating connector is formed into the base of the partial denture. As with clasp type partial dentures, precision retainers require the presence of strong teeth. Additionally, partial dentures with precision retainers are relatively expensive.
A more unconventional approach for retaining partial dentures is also known. An opening is formed in the denture base through which a single existing tooth projects. The opening is lined with a soft material that engages the individual tooth to hold the partial denture in place.